Monophasic – each pill contains the same amount of progesterone and oestrogen.Phasic – the concentrations of hormones in each pill varies with the time of the cycle.

Both monophasic and phasic pills are in a 21 day supply, with a 7 day break from days to allow breakthrough bleeding. You are still protected from pregnancy during the 7 day period, provided all the other pills were taken correctly.

EveryDay pills – 28 days supply, with 7 days of placebo pills in days 22-28. The pills must be taken in the right order.

They are available in varying strengths. The lowest dose that produces the desired effects should be used. Typically the oestrogen component is a variant of oestrogen known as ethinylestradiaol – and typically doses are 20 – 40 micrograms.

Take 21 pills and one week off (some preparations have placebo 7 days, in a 28 day packet)

Start first course on 1st day period. If starting after day 4 of period, or if miss pill >24hr time allocation must use barrier contraception for 7days.

More Info

Efficacy

Quoted as >99% effective

Described as: if taken correctly, then during the course of 1 year, <1% of women taking the COC pill will become pregnant

Mechanism

Prevents ovulation

Thickens cervical mucous

Alters uterine lining to prevent implantation

Side effects

Oestrogen increases the risk of cardiovascular disease (notably thromboembolus). It also causes:

Nausea (progesterone does not)

Progestogens can cause: headache, depression, acne, breakthrough bleeding and breast symptoms. Many of these resolve themselves after several weeks/months of treatment, and can be solved if a different progestrogen is used, however, some progestogens are also associated with increased thromboembolic risk

Thromboembolic risk – is increased in those taking the COC, particularly during the first year of use, but the risk is small, and smaller than in pregnancy (when the risk is 60 per 100 000).

In all patients the risk of thromboembolism increases with age.

There is also an increased risk of DVT when travelling (>5 hour flights) and women should be informed of and encouraged to perform inflight exercises.

Breakthrough bleeding is particularly common in the first few months, but usually resolves.

The risk of weight gain on the COC is unproven

Missing a pill

The general rule is that the combined pill can be taken within 12 hours of the usual time of administration, and still be effective.
If a pill is missed, the woman should take it as soon as she remembers, and then continue taking the rest of the pills at their normal time; even if this means taking two at once
A ‘missed pill’ is one that is >24 hours after she should have taken it

Just missing one pill is not a problem, nor is starting a new pack one day late, as long as the missed pill is taken with the next one.

The greatest risk of pregnancy if a pill is missed is at the beginning and end of a cycle.If 2 pills are missed (i.e. >24 after time should have been taken) then there is a risk of pregnancy – especially if the pill was missed in the first 7 days of the cycle.

If not, then the advice is to continue taking the rest of the pills as normal, and use an additional method of contraception (e.g. condoms) for 7 days. If this 7 days includes the 7 days ‘break’ at the end of the cycle, the next packet should be started immediately, and the ‘break’ omitted.

The patient should not take the missed pills if >2 pills were missed.

Vomiting and diarrhoea

If vomiting occurs within 2 hours of taking a pill, another pill should be taken

If there is vomiting or diarrhoea for >24 hours, then this should be treated the same as a missed pill – i.e: the pills should be taken as normal, but additional contraception (e.g. condoms) should be used for 7 days after the end of the period of illness. If this 7 days runs into the last 7 days of the cycle, the next packet of pills should be started straight away, and the ‘break’ omitted.

Drug interactions

Several drugs are known to reduce the effectiveness of the pill )’enzyme inducing drugs’). You should always check other medications the patient is on (in the BNF) before prescribing a contraceptive, and seek expert advice. Some common examples of interactions are given below:

Carbamazepine

Pheytoin

Phenobarbital

St John’s Wort

Rifabutin

Rifampicin

In women taking these drugs it is advisable to seek alternative methods of contraception

When taking a course of antibiotics – it is advisable to use condoms during the course and for 7 days afterwards.

If you pass day 21 of the packet, then start a new packet immediately, even for everyday pills.

If the course of AB’s lasts longer than 2 weeks, alternative methods of contraception should be sought

Surgery

It is advisable to discontinue all oestrogen-containing contraceptive 4 weeks before major surgery to reduce the thromboembolus risk. You can safely resume them at the first menses > 2 weeks after surgery.

Breast feeding – avoid during the first 6 months due to effects on lactation

Cautions

If two or more of the following are present, alternative contraception should be recommended

Age over 35

Obesity

BMI >39

Migraine (without aura)

BP >140/90

Smoker <40/day

FH of arterial disease

Diabetes <20y

Prescribing

Women with RF’s for cardiovascular disease should be prescribed the lowest does of oestrogen (20micrograms ethinylestradiol), or should be prescribed an alternative if >2 RF’s are present
Women >50 should not use the COC as better alternatives are available, and the cardiovascular disease risk is highInform patient to seek help immediately if:

It is ok to use two packets one after the other (i.e. start the second packet on day 22). This can be done for up to 3 months in a row. Tell the patient the lining of the womb does not keep on growing during this time!

Remember to tell patients on the everyday pill to start the new packed on day 22

Length of prescription

Normally when first prescribed, given for 3 months. After this time, BP will be checked, and if no problems or additional RF’s, then will be prescribed for 1 year at a time.

Commencing treatment

No Previous contraception

Start on day 1 of cycle, OR

If starting after day 4 of cycle, use extra method (e.g. condom) for first 7 days

Examples

Microgynon

Qlaira

Alternative preparations

Skin patch

May have a higher risk of thromboembolism than the oral preparation

Treatment consists of three patches. First patch applied on day 1 of cycle, second on day 8, and third on day 15. Remove old patch each time, and remove third patch on day 22, and have a week with no patch.

If the first patch is applied on any day other that day 1, another method of contraception (e.g. condoms) need to be used for 7 days

Withdrawal bleeding occurs during patch-free week

Vaginal contraceptive ring

A small rubber ring that can be inserted into the vagina by the patient, and then sits around the cervix. Stays in place for 3 weeks. Remove after 3 weeks, and have 1 week without ring present (similar to pill and patch)

Withdrawal bleeding occurs during ring-free week

Progesterone Only Pill (POP)

Generally used when COC is contra-indicated

Not as effective as COC, although still >99% effective

Often used in those on COC before / during / after surgery

Summary

CONTRACEPTION

PROGESTERGONE ONLY PILL

EFFECTIVENESS

99% effective when used correctly

PREPERATIONS

Cerazette, Mini Pill

HOW IT WORKS

Thickens cervical mucus,

thins lining of womb,

Higher dose pop ie. cerazette also inhibits ovulation

ADVANTAGES

Can be taken in those with CI to COC ie. breastfeeding, older women, cardiovascular risk, DM

Advantages of POP over COC

Prescribing

Time window for admission during which the pill is effective is small (3 hours). However, the pill Cerazette allows a 12 hour window, similar to COC. Sometimes the regular (3hr window) POP is called the Mini Pill.

Starting treatment

Start on the first day of the cycle. If started within the first 5 days, protection is immediate
If started after day 5, use condoms or another contraception for 2 days

Those with a short menstrual cycle (<23 days) may not be protect if they start on day 4 or 5, as ovulation may occur early. Advise condoms for 2 days after commencing POP

After miscarriage / abortion

If <24 weeks, start straight away

If >24 weeks seek advice

After Pregnancy

Does not interfere with lactation, or increase the risk of thromboembolic event, and thus can be start straight after pregnancy

A small amount of progesterone does enter the breast milk, but this does not cause any adverse effects in the child

If started after 21 days after birth, use an additional method of contraception for 2 days

Missed pills

Take the missed pill and the next pill s soon as you remember. If the missed pill was >3 hours late (12 hours for cerazette), then you are not protected, and condoms should be used for 2 days.

Emergency contraception is recommended if unprotected sex has occurred during this two day window

Vomiting and diarrhoea

If this occurs within two hours of taking the pill, use condoms or another method of contraception for 2 days after

Interactions

Fewer than COC – e.g. antibiotics are generally not a problem, however, any liver enzyme inducing drugs may still interact.

Additional contraception (e.g. condoms) should be used during treatment with the enzyme inducing drug, and for 4 weeks after

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Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009.
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